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unnecessary-empty-iterable-within-deque-call (RUF037)

Preview (since 0.9.0) · Related issues · View source

Fix is sometimes available.

This rule is unstable and in preview. The --preview flag is required for use.

What it does

Checks for usages of collections.deque that have an empty iterable as the first argument.

Why is this bad?

It's unnecessary to use an empty literal as a deque's iterable, since this is already the default behavior.

Example

from collections import deque

queue = deque(set())
queue = deque([], 10)

Use instead:

from collections import deque

queue = deque()
queue = deque(maxlen=10)

Fix safety

The fix is marked as unsafe whenever it would delete comments present in the deque call or if there are unrecognized arguments other than iterable and maxlen.

Fix availability

This rule's fix is unavailable if any starred arguments are present after the initial iterable.

References